Semantic dementia, otherwise known as the temporal variant of frontotemporal dementia, is characterized by a progressive loss of semantic memory, or general knowledge about the world. Afflicted patients gradually lose the ability to identify objects, people, and ideas. Some research has shown that the disorder also affects autobiographical memory--in other words, memories for everyday life-but the nature, extent, and neuroanatomical substrate of this loss are not well understood. Specifically, some research has shown that the memory loss in semantic dementia is temporally graded-that is, recent memories are recalled better than remote memories. These studies have primarily used verbal cues, however, and we do not yet know whether other cues might prove more effective. To this end, we will cue participants' autobiographical memories using words, pictures and odors. Odors are chosen because they are a particularly good cue for early autobiographical memories (which are just the memories lost in semantic dementia) and they depend upon medial temporal regions that are intact in semantic dementia. In addition, we will conduct a longitudinal study of semantic dementia to characterize the rate and extent of memory decline. Overall, an investigation of the effects of modality, both in cross-sectionally and longitudinally, will help us understand the role of the anterolateral temporal cortex in memory, the relation between semantic and episodic memory, and the precise nature of the autobiographical memory deficit in semantic dementia.